Video displays have historically updated all picture elements (pixels) of a display frame by frame employing raster scanning, whereby all display pixels are updated and refreshed in one (progressive) or two (interleave) passes at a frame rate sufficient to maintain the realistic illusion of movement that video is designed to convey. A composite frame of multiple images has to have been composed prior to transmission to the display: a single full frame is transmitted to the display each scan update. For example, picture-in-picture analog television display was accomplished by overlaying multiple video image frame buffers into a single frame buffer, and then that single frame transmitted and displayed on a raster-scanned video display.
Historically, video transmission as well consisted of successive full frames. As a means to compress data for transmission, recently developed video formats such as MPEG use partial frames, though those partial frames are transposed into full frames prior to display on the target device, as the display device itself is designed exclusively for full frame updating.
The 1999 second edition of “DTV, The Revolution in Digital Video” by Jerry Whitaker characterizes current television technology (page 376): “The cathode-ray tube (CRT) has remained the primary display device for television since electronic television was developed in the 1930s. It survived the conversion from monochrome to color television, but it may not survive the cessation of analog television broadcasting. The CRT is fundamentally a 3-dimensional structure and, as such, is limited in the size of image available on direct-view tubes . . . . Although project displays can provide extremely large images, they too are 3-dimensional boxes, which in many homes are simply unacceptably large.
“It is undeniable that great progress has been made in solid state displays of various designs over the past few years . . . . While promising new products continue to be developed with each passing year, the hang-it-on-the-wall display is still (at this writing) perhaps five years away. Having said that, it is only fair to point out that such devices have been about five years away for the past thirty years.”
The Dec. 9, 2000 Economist magazine wrote of the portents of change in digital display technology: “Kent Displays is working on “cholesteric” liquid crystals—so-called because the liquid-crystal material is made from cholesterol. The cholesteric-LCD is chemically altered so that it is bi-stable, being reflective or non-reflective depending on the direction of the electric current applied to its surface.
“Ingeniously, Kent makes three versions of the display, which can reflect red, blue or green light—the primary colors from which all others are composed. By stacking the three versions as a sandwich, the company can produce a highly reflective 4,000-colour display with a contrast ratio as good as ink on paper . . . . As it can be switched from reflective to non-reflective in a brisk 30 milliseconds, Kent's colour display can also show videos . . . .
“Although getting better all the time, display technology—and the related constraint of battery life—has been a limiting factor in the development of portable consumer electronics. That is because existing displays have to be refreshed continuously. Researchers reckon that, all things being equal, bi-stable displays consume less than a hundredth of the power used in refreshed displays. That could translate into either much smaller batteries or a much longer period between charges.”
Another article in the Jun. 2, 2001 Economist magazine touts the imminent commercialization of displays based upon optical light-emitting diode (OLED) technology: “Barry Young of DisplaySearch, a market-research firm based in Austin, Tex., claims that 30 firms have announced plans to produce OLED displays . . . .
“Since the current controlling an OLED can rapidly be “toggled” on and off, individual picture elements (pixels) on a screen can change their appearance fast enough to handle a stream of video or web images without leaving irritating after-images on the screen.”
Recent advances in display technology suggest commercially viable high resolution digital video displays are forthcoming. As new digital display device technology fundamentally differs from its historical antecedents, display resolution and size, power consumption, and other cost and performance related considerations suggest an alternative to conventional raster scanning technology.